## Description:

The method that I used to decipher this note is Caesar cipher. First, I tried out by minus the alphabet by 1. But I could not get the answer. Then I try to without the alphabet one by one until 7 and then I got the solution, I conclude that each notice in this concept subtract by 7 is the solution.

The table used to decipher this communication is show as below:

Cipher Text

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Plain Text

t

u

v

w

x

y

z

a

b

c

d

e

F

g

h

i

j

k

l

m

n

o

p

q

r

s

## 2.

EDHBPVMVPUVOPAFVOEAMHDYHRVFHBOYHRPKANQKPOPKBPXVQKPYHMHDKBMHCHHYSBDPAIUANCHIADH

## Plain Content material:

creativityistodiscovernewideasnewthoughtsthatmightneverhavebeenpartofyoubefore

(creativity is to find new ideas new thoughts that might never have been part of you before)

## Description:

First, I tried to decrypt this subject matter with Caesar Cipher. I tried to shift all the characters in this note for 25 times but I possibly could not decipher this subject matter.

So I tried out to decipher this question with mono-alphabetic substitution method. I tried to solve it by software called "Secret Code Breaker Monoalphabetic Substitution Solver" and I got a English phrase which is readable after i add spaces to split up each word in this message.

The concept employed by this software to solve the cipher content material is by evaluating what in the cipher content material with the British dictionary repository.

The answer key given by the program to solve this question is below:

Cipher Text

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Plain Text

o

a

b

r

c

d

l

e

f

k

h

z

v

u

s

t

g

w

p

q

y

i

j

m

n

s

The snapshot of this program:

## 3.

HELMADINEARTHOTSUCIUDOTYR

## Plain Wording :

## 4.

LKHYVLHYPPALGBOGLVOGLGOGLPKGPEANJFANPOGLGYDOGLPKGPVHM

HBOGLYALVUDANQAPALGBOGLGYFOHHGOGLPKGPEANJFANPOGLPKHO

GLVOGLVFJVWHPAOHHDANBOGLOGL

## Plain Text :

## 5.

DQPTAZJWB ZKFQGM NZJYY GQDCN

## Plain Word:

couldhant hefori shapp rocks

so I analysis

computing theory still rocks

## 6.

## Plain content material:

A PIGPEN GOES OINK WHEN IT WRITES

## Decription:

The method that I used to decipher this message is to apply pigpen cipher.

First, I really do the study on what are the types of cipher text available and discovered this cipher text message is pigpen cipher at the next website.

http://en. wikipedia. org/wiki/Substitution_cipher

http://upload. wikimedia. org/wikipedia/commons/thumb/3/36/Pigpen_cipher_key. svg/220px-Pigpen_cipher_key. svg. png

After knowing which kind of cipher text used in this question, I used the diagram above to decipher each notice in this message and got the answer.

## Question 2:

a) How many possible mono-alphabetic ciphers are there? Show your reasoning.

## Answer:

Mono-alphabetic cipher means that we now have no two letters that happen to be encoded to the same letter and each letter can't be encoded as itself.

Since there are 26 alphabets, therefore the first alphabets will have 25 possible alphabets to be replaced. After that, another alphabets will have 24 possible alphabets to be changed. The range of possible alphabet is reduces appropriately. So the range of possible cipher are N(N-1)(N-2). 2*1 where N = 25 or 25!.

25!

= 25 x 24 x 23 X 22 x 21 x 20 x 19 x 18 x 17 x 16 x 15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1

= 1. 551121004 x 1025

Therefore, there are roughly 1. 551121004 x 1025 possible mono-alphabetic ciphers there.

b) Let's assume that it is possible to test 1 billion possible ciphers per second, analyze how long it would take test all possible mono-alphabetic ciphers.

## Answer:

25! / (1 x 109)

= 1. 551121004 x 1016 seconds

(1. 551121004 x 1016 ) / (60x60x24x365) = 4. 91857243 x 108 years

Therefore, it could take about 4. 91857243 x 108 years to test all possible mono-alphabetic ciphers.

c) Notice that there are just 14 different characters in the encrypted concept. Just how many possible decryptions there are of the communication? (Hint: As 'J' will not come in the ciphertext, it doesn't matter what letter it is encrypted from).

## Answer:

Since there are 14 letters in the meaning, so the variety of possible letters for the first letter to be replaced is 25. Then the number of possible characters for second words is 24 characters and so on until it extends to the 14th letter.

25 x 24 x 23 X 22 x 21 x 20 x 19 x 18 x 17 x 16 x 15 x 14 x 13 x 12

= 3. 885885152 x 1017

So there are around 3. 885885152 x 1017 different ciphers.

d) Supposing, as before, than you can attempt 1 billion possible codes per second, analyze how long it would take to test all possible decryptions of the message.

## Answer:

3. 885885152 x 1017 / (1x 109)

= 3. 885885152 x 108 seconds

(3. 885885152 x 108) / (60 x 60 x 24 x 365)

= 12. 32206 years

Therefore, it could takes approximately 12. 32206 years to test all possible decryptions of the message.

e) How many possible decryptions of this message is there if you are told the

following partially complete stand?

## Answer:

Since 5 words has already been known, therefore the remaining variety of possible decryption for the 6th letter is 20, 7th characters is 19 and so forth until 14th which is 7.

20 x 19 x 18 x 17 x 16 x 15 x 14 x 13 x 12 x 11 x 10 x 9 x 8 x 7

= 3. 379030567 x 1015

f) If you're told that the concept probably contains the name of an Australian city and a university or college, how much more of the stand can you complete? Is it possible to completely decipher the message? Why or you will want to? Discuss your answer.

## Answer:

There are five characters which have already given as below:

Encrypted letter

X

F

Y

Z

W

Plaintext letter

M

E

L

B

I

From the table above, possibly the name of the Australian city is "MELBOURNE" and it fit exactly as "XFYZABCDF".

So, from the information above. I could conclude the table below:

Encrypted letter

X

F

Y

Z

W

A

B

C

D

F

Plaintext letter

M

E

L

B

I

O

U

R

N

E

Now I substitute the plaintext letter in to the encrypted concept.

P

X

W

Q

W

U

Z

T

U

F

V

W

D

X

F

Y

Z

A

B

C

D

F

M

I

I

B

E

I

N

M

E

L

B

O

U

R

N

E

"PXWQ" seem to be to be the name of the college or university in Melbourne which is "RMIT".

So from the result above, I try to decipher the subject matter with the next attempt to make the subject matter make sense:

Attempt 1: Replace "P" as "R"

Attempt 2: Replace "U" as "S".

Attempt 3: Replace "Q" as "T".

Attempt 4: Replace "T" as "A"

Attempt 5: Replace "V" as "D"

And now I'll get the result and below:

RMIT IS SITUATED IN MELBOURNE

HOWEVER, from the effect above, R is encoded into 2 characters above which is "P" and "C".

Since there are no notice can encoded to 2 words, So I figured this message can't be completely decipher.

## Question 3:

There are a number of available source encryption softwares/systems available online. Which system(s)/software(s) can you recommend and why?

## Answer:

There is a number of available source encryption software or systems available over the Internet that delivers data safety such as TrueCrypt by TrueCrypt Groundwork, DiskCryptor by ntldr, Crosscrypt by Stefan Scherrer and FreeOTFE by Sarah Dean. Based on the research I did so from the internet, I came across that the TrueCrypt is the most popular open source encryption software which runs on all of the major platforms such as Windows XP/Vista/7, Mac OS X and Linux. However, I'd like to recommend FreeOTFE due to its different advantages over other available sources encryption software.

The first reason why I recommend FreeOTFE is because it is highly portable. Unlike other encryption system, FreeOTFE offers FreeOTFE Explorer which allows FreeOTFE volumes to be accessed without setting up it or any device drivers. Besides that, administrator rights are not required for an individual to use this lightweight FreeOFTE. This feature makes it ideal and convenient for use with the removable multimedia or USB drives so that individual can make use of it to encrypt their data with any supported computer. For example, user may use FreeOTFE in internet cafes where computer can be found but not granted with administrator privileges. Unlike other software which administrator protection under the law and installation must run the program, so I think FreeOTFE is a better choice compare to them.

Besides that, FreeOTFE facilitates a whole lot of ciphers and hash algorithms. The ciphers it implements include AES, Blowfish, Ensemble5/CAST6, DES/Triple DES, MARS, RC6, Serpent and Twofish.

It facilitates hash algorithms such as MD5, RIPEMD320, SHA512, Tiger, Whirlpool and so many more.

Its cipher methods supported include XTS, LRW and cipher-block chaining (CBC) which including XTS-AES-128 and XTS-AES-256. In addition, it offers security tokens or smartcards recognized for extra security. Comes even close to TrueCrypt, TrueCrypt only supports SHA-1, RIPEMD-160, Whirlpool hash algorithms and fewer ciphers than FreeOTFE.

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-still under mantainance